Abstract

The nano-size gold loaded visible light driven Au-TiO2 nanophotocatalysts were synthesized using a commercial sonicator bath producing 42 kHz ultrasound. The X-ray diffraction (XRD), transmission electron microscopy (TEM) and high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) analyses revealed the gold nanoparticles incorporated in the TiO2 resides at the surface of the nanocatalysts. An increased BET surface area was observed for the Au-TiO2 when compared with the bare TiO2 Which gave the first notation that the gold nanoparticles modified the physicochemical characteristics of the TiO2. The RAMAN spectrum shows the shift by 5 cm(-1) at 639 cm(-1) which indicated that the loaded gold nanoparticles were loaded on the surface of TiO2 nanoparticles and thus confirms that the gold nanoparticles readily accepts the electronic charges created during the photoexcitation of Au-TiO2 nanocatalysts. The Simazine (triazine based pesticide) was taken as the model pollutant to evaluate its sonocatalytic, photocatalytic and sonophotocatalytic degradation in the presence of TiO2 and Au-TiO2 nanocatalysts. The first order kinetics was observed for the Simazine degradation. The observed rate constants indicate that the order of degradation of Simazine was, sonophot-ocatalysis > sonocatalysis > photocatalysis. The additive effect was observed for the Au-TiO2 assisted sonophotocatalytic degradation of Simazine. A 1.65 and 1.38 fold enhanced mineralization was achieved for the sonophotocatalytic degradation of Simazine when compared with the photocatalytic and sono-catalytic processes. The intermediates produced during the mineralization of Simazine were analyzed using ESI-MS analysis and based on that a suitable mechanism has been proposed. (C) 2014 Elsevier B.V. All rights reserved.